The invention relates to a method for hard fine machining of the toothing of a gear or of a gear-like profile of a workpiece, wherein the gear or the workpiece has an axis of rotation, wherein at the method the toothing of the gear or the gear-like profile of the workpiece is machined with a hard fine machining tool, wherein the hard fine machining tool has an axis of rotation and rotates around the same during hard fine machining.
The final grinding process has a high importance especially at the production of gears. At this process the tooth flanks are subject to a grinding operation by which the flanks are brought to the precise shape. An efficient process at the production of the toothing is the generative grinding by means of a grinding worm or the profile grinding with a profile grinding wheel.
A method of the kind mentioned above is known from DE 10 2010 005 435 A1. Here, at first a rough machining and then a finish machining is carried out at a workpiece to machine a toothing which is arranged in a face region of the workpiece, wherein the tool spindle is pivoted between the two process steps to avoid collisions.
Further pre-known solutions are shown in WO 94/19135 A1, in U.S. Pat. No. 6,402,607 B2 and in U.S. Pat. No. 3,708,925.
It is known for the optimization of the surface of the flanks of the toothing to carry out beside the grinding process as such afterwards a fine grinding process or a polishing process. Such a fine grinding process or polishing process is also called a polishing grinding process and is a subsequent machine finishing process by which the quality of the surface of the toothing can be increased. It is the aim of the machining at said fine grinding or polishing process to increase the surface quality and the percentage contact of the tooth flanks by an only minor amount of removal.
Thereby, a multi-step process is employed at which at first a conventional generative grinding or profile grinding process is carried out and subsequently the mentioned fine or polishing grinding follows. Thereby, two different tool specifications are used which differ from another only marginal or not a bit with respect to their tool shape or profile. Often, both regions for the generative or profile grinding at the one hand and for the fine or polishing grinding at the other hand are arranged at one and the same tool carrier and firmly connected with another (e. g. glued or screwed). Preferably, both machining zones are then at first (in the case of a dressable tool) collectively dressed. Subsequently, the fine grinding and polishing tool respectively can also be slightly modified by a further profiling; thereby for example a reduction of the outer diameter can take place. At the subsequent machining the two mentioned zones are then used successively, wherein however in principle the same tool settings and especially the same pivot angle of the tool are used.
Thereby it is possible to realized corrections at the fine grinding and polish grinding respectively. Known possibilities of correction are the pivoting of the workpiece axis to reduce an infeed rate and the polishing pressure respectively at one of the tooth flanks and to increase the same at the other flank as well as changing of the distances of the axis which then acts on both tooth flanks equally at symmetrical profiles.
However, often detrimentally the roughness in the tip and in the base of the toothing is different what is not desired. The mentioned pre-known possibilities for correction can solve this problem only limited. So, for example a reduction of the distance of the axis increases the machining forces and causes possibly an undesired discrepancy in the shape.
Furthermore, it is detrimental that the known solutions are very time consuming because different working steps for the setting are necessary, wherein however the desired results are often not reached.
Furthermore, it is detrimental that the obtained results are often compromises with respect to the geometry of the created tooth flank.